The present invention is directed to circuit interrupters, and more particularly to a return spring for a circuit interrupter operating mechanism.
Commonly, multiple contacts, each disposed within a cassette, are arranged within a circuit breaker system for protection of individual phases of current. The operating mechanism is positioned over one of the cassettes and generally connected to all of the cassettes in the system.
Circuit interrupter operating mechanisms are used to manually control the opening and closing of movable contact structures within circuit interrupters. Additionally, these operating mechanisms in response to a trip signal, for example, from an actuator device, will rapidly open the movable contact structure and interrupt the circuit. To transfer the forces (e.g., to manually control the contact structure or to rapidly trip the structure with an actuator), operating mechanisms employ powerful springs and linkage arrangements. The spring energy provides a high output force to the separable contacts.
A circuit interrupter operating mechanism utilizes a handle to indicate whether the circuit breaker is in the xe2x80x9conxe2x80x9d, xe2x80x9coffxe2x80x9d or trip condition. When the movable contact structures are closed, the circuit breaker is xe2x80x9conxe2x80x9d. Conversely, when the movable contact structures are open, the circuit breaker is xe2x80x9coffxe2x80x9d. When the circuit breaker trips due to an overload condition, the handle is intended to indicate that a trip has occurred by moving to an intermediate position located between the xe2x80x9conxe2x80x9d and xe2x80x9coffxe2x80x9d positions. Typically, when a circuit breaker is tripped, the force applied to the handle by the springs is low. This is partly due to compact circuit breaker designs as well as the need to trip the circuit breaker should the handle be blocked. Because of the low force applied to the handle when the circuit breaker is tripped, it may not be visually obvious that the circuit breaker tripped. The handle may not be in a readily identifiable intermediate position.
In an exemplary embodiment of the present invention, a return spring mechanism is arranged to operate with a circuit breaker operating mechanism during a trip condition. The operating mechanism is movable between a tripped position, a reset position, an off position and an on position. The return spring mechanism is attached to the exterior of the circuit breaker frame and includes a return spring. A handle yoke is pivotally connected to the frame. A spring is configured to move the handle yoke a first distance when the operating mechanism in a tripped condition. The return spring is arranged to move the handle yoke a second distance when the operating mechanism is in a tripped condition. The movement of the handle yoke a second distance provides clear indication that the circuit breaker is in the tripped condition.